1. Field of the Invention
The present invention relates generally to valves and, more particularly, to a valve assembly wherein a heating modality or device is cooperatively engaged to a prescribed location on a valve housing or body of a valve to effectively maintain the temperature of the valve above the saturation temperature of the related system pressure for purposes of avoiding the accumulation of condensate in the interior of the valve body and/or on other internal structural features thereof.
2. Description of the Related Art
A common application for the use of industrial control valves is steam control. In this regard, steam control valves are generally considered to be one the most basic and indispensible components of steam systems. In many process applications, steam control valves not only control pressure, but also temperature. Additionally, steam control valves can be used simply as an on and off device, or any combination of controlling to include regulation, modulation, mixing, or even isolation.
Many currently known steam control valves work in accordance with an operational principle wherein they are closed in normal operating conditions and under working pressure. In this state, medium pressure acts on the piston of the valve in a manner maintaining the valve in a closed position or condition. In these types of valves, an ancillary device such as a pilot valve is often used to open a discharge path which facilitates the release of steam out of the valve piston chamber of the valve. The steam release resulting from the opening of the pilot valve, and the resultant reduction in the pressure acting on the valve piston (which otherwise maintains it in the closed position), facilitates the actuation of the valve to its open position or condition.
However, with regard to steam control valves which operate using the discharging principle, there is a tendency for such valves to develop condensate on the inner or interior surfaces of the valve body, within the piston chamber, and/or on other internal structural features thereof. Though in the prior art it is known to insulate the aforementioned steam control valves, the formation of the condensate still typically results since the valve cannot be ideally insulated, with insulation imperfections typically resulting in an escape of heat from the valve. When this occurs and the valve temperature falls to or below the saturation line or temperature of the related system pressure, the heating of the valve by the steam itself results in the above-described condensate formation within the valve. Another cause of condensate formation is attributable to transients pertaining to valve temperature. In this regard, since steam control valves are typically very large and heavy, the valve temperature, which is usually connected to internal pressure, will not immediately follow the pressure change, but rather will remain at an established level for a longer period of time. This occurrence often results in the generation of condensate, since if a change in the valve temperature does not immediately follow a pressure change, the valve temperature will usually fall below the aforementioned saturation line.
The formation of water or condensate on the interior surfaces of the valve body, within the piston chamber, and/or on other internal structural features of the valve gives rise to certain valve performance penalties. More particularly, the condensate adds to the volume (compared to steam only) which needs to be released by the discharge path opened by the pilot valve, thus decreasing the opening time of the valve. In this regard, once the discharge path is opened, the water/condensate evaporates and consequently a much larger steam volume needs to be discharged, compared to the state that would otherwise exist if only steam was present in the piston chamber in accordance with the normal operational parameters of the valve. The present invention addresses and overcomes this particular problem by providing a valve assembly which is provided with a modality to facilitate the heating of the valve in a manner prohibiting the generation of condensate, thus keeping the valve internals free of condensate and avoiding the performance penalties attributable thereto. These, as well as other features and attributes of the present invention, will be discussed in more detail below.